He continues: "The less money you have, the more likely someone will come at you with some scheme. … Please ignore them. Always remember this: If a deal is a great deal, they aren't going to share it with you."

Cuban doesn't broadcast his deals and he suggests being skeptical of anyone who does. "I keep them all to myself," he writes. "If the person selling the deal was so smart, they would be rich beyond rich rather than trolling the streets looking to turn you into a sucker.

"The money is made in investments by investing," Buffett told CNBC in 2016, "and by owning good companies for long periods of time. If they buy good companies, buy them over time, they're going to do fine 10, 20, 30 years from now."